(1) Field of the Invention
The present invention relates to the recycling or digestion of used fluorescent tubes. More particularly, the present invention relates to a combined crushing and separation system in which a clean separation is made between the crushed glass and the potentially toxic fumes and powders contained within the interior of fluorescent tubes. More particularly still, the present invention relates to agitation and abrasion of the glass particulates derived from used or burned out fluorescent tubes after fracturing such tubes by a prior fracturing apparatus to effect a superior separation of powder material adhering to the already fractured glass particulates derived from such sections of burned out tubes.
(2) Discussion of the Prior Art
Fluorescent light tubes are formed from elongated cylindrical or tubular glass receptacles which are charged with mercury or other conductive vapors. The inside surface of the tube is coated with a fluorescent coating of some form such as phosphorus itself or other phosphor powders such as antimony, beryllium, cadmium and strontium compounds plus in some cases lead and the like. Mercury vapor as well as beryllium, strontium, lead and cadmium are well known as potentially toxic materials as are other phosphor powders with which the inside of a fluorescent tube may be coated. Older fluorescent tubes often used fairly high concentrations of beryllium powders, but this has been, in general, superseded in more recent fluorescent tubes by cadmium-type powders.
Since fluorescent tubes are in general, bulky and unsatisfactory for disposal without treatment, it has become customary to crush them into small pieces by various means and then dispose of the fractured pieces. Merely fracturing the tube itself into small pieces for disposal, however, is not very satisfactory because of the potentially toxic nature of the dust and vapor originally confined inside the fluorescent tube. Such potentially toxic particulates, which occur mostly in the form of small dust particles plus mercury vapor and small drops or beads of mercury, can be quite detrimental if they escape to the environment.
While it might be possible to refurbish burned out fluorescent tubes by removing the metal ends or "tips" from the tubular glass envelope and cleaning the inside followed by recoating the inside of the tube with fluorescent or phosphor powder material, followed by the addition of new tips and recharging with conductive metallic vapor, as a practical matter, the cylindrical glass container itself has little intrinsic value. Furthermore, it is difficult to properly renew the internal fluorescent surface of the tube and difficult to reapply the metallic tips to form an effective seal with the ends of the tube. It is usually more economical, therefore, to manufacture new fluorescent tubes than to refurbish worn out tubes. It has consequently become customary to dispose of the used tubes. However, because of their bulky nature, it is difficult to adequately dispose of the tubes except by crushing to reduce their bulk followed by disposal of the residue in a hazardous material landfill or dump site or the like. While it has been recognized the toxic particulates and vapors should be contained somehow, the usual manner of handling the toxic dust and vapor has been either to ignore it or to crush the tubular receptacle while washing by means of a flow or stream of water to prevent the escape of toxic material to the environment. Ignoring the toxic materials is no longer either acceptable or possible. Wetting down the crushed glass and other materials, on the other hand, creates what can only be referred to as a "soggy mess" which not only is difficult to dispose of, but weight-for-weight has become heavier and even more difficult to dispose of than the original dry material, particularly in view of its toxic nature.
It has long been known to provide apparatus for breaking or crushing glassware and particularly glass bottles and the like to reduce their bulk and incidentally to prevent their reuse particularly in the case of liquor bottles and the like. Among such apparatus may be mentioned the following patents described in the present Applicants' previous applications referred to above:
U.S. Pat. No. 2,185,352 to C. F. Peters
U.S. Pat. No. 2,558,255 to N. E. Johnson et al.
U.S. Pat. No. 3,353,756 to D. J. Morgenson
U.S. Pat. No. 3,655,138 to G. A. Luscombe
U.S. Pat. No. 3,889,886 to J. D. Spivey
While it has been known, therefore, generally to crush glassware by mechanical crushing means in order to decrease its bulk prior to disposal, the crushing of glass bottles and the like and the crushing of glass receptacles containing hazardous materials such as fluorescent tubes and the like is something quite different. Hazardous materials such as the toxic phosphors coating the inside of fluorescent tubes or the mercury vapor trapped in the tube adds an entirely new dimension to the problem. A number of devices, machines and/or systems have been suggested or developed for the crushing of fluorescent tubes in order to decrease their bulk. Some of such devices are the following:
U.S. Pat. No. 2,593,657 issued Apr. 22, 1952 to A. J. Coon et al. discloses a reciprocating-type crusher designed to crush fluorescent tubes and the like. Coon et al. discloses that during crushing of the tubes the beryllium compound that adheres to the inner walls of the tube as a layer of dust has a tendency to become suspended in the surrounding air. Coon et al. attempts to alleviate this problem by providing an exhaust for air withdrawn from the treatment or fracturing zone and releasing such air "to the outer atmosphere whereupon it is safely dispersed into space". Coon et al. also discloses that he uses an airtight casing so there is as little escape of air and dust as possible until the air stream is discharged to the outer atmosphere. While Coon et al. uses an air stream to remove toxic materials from the tube fracturing zone of the machine, there is no evidence that Coon et al. recognized how to effect a reasonably clean separation between the toxic materials and the glass particles.
U.S. Pat. No. 2,620,988 issued Dec. 9, 1952 to E. H. Tellier discloses a fluorescent tube chopping device arranged for continuous flushing of the fracturing zone with a stream of water to flush the toxic materials from such fracturing zone. There is no separation between the potentially toxic dust and the crushed pieces of glass, both being collected in a lower removable receptacle. Because the potentially toxic materials are not removed from the glass particulates, the materials cannot be used again.
U.S. Pat. No. 2,628,036 issued Feb. 10, 1953 to J. B. Hall discloses a fluorescent lamp disposal arrangement in which fluorescent tubes are passed lengthwise down a tubular inlet at the bottom of which the fluorescent tubes are progressively fractured into pieces by a rotating hammer arrangement. A large suction fan is arranged at the top or upper end of the system and a water inlet is arranged just above the chopper blades. During operation of the device, therefore, there is a countercurrent flow of material through the apparatus with fractured tube material traveling downwardly together with flushing water or other material and the air stream passing upwardly to draw out gases. The fractured glass and metal may be separated from the water containing the toxic beryllium powder by means of a screening arrangement down which the water and fractured glass material pass and the metal tips derived from the tubes separated from the fractured glass by magnetic means. The air stream does not pass between the fractured glass particulates, but merely over them.
U.S. Pat. No. 2,866,604 issued Dec. 30, 1958 to J. B. Hall discloses a fluorescent tube disposal device including a rotary breaker arm disposal arrangement bathed in water during actual breaking of the fluorescent tubes. Hall uses a magazine to contain the fluorescent tubes and provides for a draft of air to be drawn through the magazine during use.
U.S. Pat. No. 3,913,849 issued Oct. 21, 1975 to I. M. Atanasoff et al. discloses a fluorescent tube digester or breaker. The Atanasoff et al. device is made to fit on the top of a barrel and to draw air downwardly through the chamber and out the usual bung hole where there is provided a surface filter arrangement to remove phosphorus and mercury from the air stream.
U.S. Pat. No. 4,545,540 issued Oct. 8, 1985 to A. Nakamura discloses a device for breaking up fluorescent tubes within a large open casing. The fractured particulates fall straight down and are collected in the bottom of the apparatus while an air stream is drawn off from the side to remove environmentally harmful substances namely toxic dust and powder particulates. Little attempt appears to be made to effect a separation between the toxic particulates and the glass. A vacuum stripping system is used. However, the principle aim appears to be to draw off gaseous and other contaminants and separate them from the air stream in order to prevent injurious substances from leaking from the apparatus and contaminating the environment.
U.S. Pat. No. 4,579,287 issued Apr. 1, 1986 to W. E. Brown discloses a chain flail-type tube crusher for fluorescent tubes. The crushing or breaking occurs in a closed barrel-type environment and the debris is deposited into a plastic bag-type liner without any attempt to separate the glass components from toxic dust or powder components or even to draw off harmful mercury vapors.
U.S. Pat. No. 4,607,798 issued Aug. 26, 1986 to K. F. Odlin discloses a lamp crushing apparatus having a special non-jamming crushing blade which is bathed in water sprays during operation to remove or absorb toxic materials. A forced draft of air also appears in one embodiment to circulate past the rotating blade from the side. The air drawn off is not filtered, but the wash water is filtered as it runs off. The Odlin device crushes not only fluorescent tubes, but also sodium lamps and the like.
U.S. Pat. No. 4,655,404 issued Apr. 7, 1987 to J. W. Deklerow discloses a portable flail-type fluorescent tube crusher for breaking fluorescent tubes. The device includes a filter system making use of an exhaust fan for generating a vacuum in the crusher housing to draw off toxic gases including mercury and pass them into a treated charcoal filter to absorb the mercury vapors.
While the prior devices noted above have enjoyed at least a modicum of success, serious problems and inconveniences have persisted. In particular, the separation between the toxic materials and the supporting and confining materials has not been sufficient to allow such supporting and confining materials, i.e. essentially the glass, to be disposed of or reused without special precautions because of hazardous inclusions. Furthermore, the toxic material, i.e. the mercury, antimony, beryllium, cadmium, strontium and other fluorescent materials, as well as other materials such as lead and the like originally contained within the tubes, have not been separated sufficiently from the supporting and confining materials, i.e. the glass, to allow either handling in a relatively constricted volume and/or any sort of reasonably effective partial or complete recovery. The most successful systems, furthermore, have incorporated a washing step. Washing, however, creates a large volume of polluted water which must then be dealt with in turn and in addition, creates wet, heavy and often sticky materials that are inherently difficult to handle and/or dispose of. There has been, consequently, a definite need for a method and means that is economical, convenient and effective in treating or digesting used fluorescent tubes and that makes an effective separation of the toxic materials from the supporting and confining materials by a dry separation process and means.
U.S. Pat. Nos. 5,042,724 and 5,092,527 issued respectively on Aug. 27, 1991 to T. Perry, the present inventor and Mar. 3, 1992 to T. Perry et al. disclose the fracturing of used fluorescent tubes into small pieces followed by countercurrent stripping of the fractured glass particulates with a stream of air as well as jarring of the glass particulates as they pass through the countercurrent stripping zone. The apparatus and methods of these patents have considerably improved the efficiency and effectiveness of the treatment and recovery of the components of used fluorescent light tubes. However, it has been recognized that there remains still further room for improvement. While the separation between toxic materials and fractured structural materials, i.e. glass particulates, is very effective in the invention described in the Applicant's prior patents, a complete or 100% separation has not been found possible. Consequently, there is a need for a redundant or further improved separation of the glass particulates and the objectionable powder and vapor-type materials originally included with them.